What is up with my gauges?

[f-two-fiddy]

So, I replaced the front fuel sending unit when I bought my truck. 7 years later it no workie any more. And, the rear gauge reads high when full, and is empty before the gauge reads empty.

The temp gauge seems to be reading slightly higher than normal, and the oil gauge reads a little lower than it used to. (I've modified the OP gauge to use the old time sender and read real pressure)

Any idea's???

 

[yARIC008]

Seems like the only thing all that would have in common would be the ground. Maybe you need to find the ground wire to the cluster and check its continuity.

 

[icanfixall]

Ground wire was my first guess too. They can be very difficult to find if they are an intermittent fault..

 

[snicklas]

According to his signature, his truck is an 85, so it still has the IVR - Instrument Voltage Regulator. The gauges in these trucks, are a 6 volt gauge, and the IVR is a 50% duty cycle "switch". So it is on supplying voltage half the time, and its off the other half. So, when it's working properly the gauges show their "normal" level. The IVR can stick, and supply voltage all the time, so the gauges will read high..... so this may be the issue..... It's not uncommon to be driving down the road, hit a bump, and all the gauges start to read high (Normally you only notice the temperature gauge the first couple of times) hit a bump, or thump the dash and they all settle back to where you expect to seem them. I would say if all gauges are reading high, I would look into the IVR on the back of the instrument cluster. It's a little silver box, and not all that expensive.......

 

[f-two-fiddy]

Actually, I have two IDI's.

It's the '93 that is buggin me.

 

[f-two-fiddy]

So, does anyone have an idea where the OBS instrument cluster actually grounds too?

 

[cpdenton]

On OBS trucks, there are ground wires coming out of both of the plugs on the back of the instrument cluster, and they all go down to a green bolt behind the drivers side kick panel.